The prior art has used asbestos, carbon and graphite short straight staple felts, and various ceramic materials, particularly ceramic foams as thermal insulation having fire blocking properties. The bulk densities of some of the well known thermal insulating materials are in the range of 0.35 to 2 pounds per cubic foot (5.6-32.04 kg/m.sup.3) for insulating materials useful at temperatures not exceeding 120.degree. C., and from 2 to 5 pounds per cubic foot (32 to 80 kg/m.sup.3) for the high temperature (about 3000.degree. F.) insulating materials. Even the newest "light weight" insulating material recently disclosed comprising a ceramic from which a carbonaceous material has been burned out has a bulk density of about 2 to 6 pounds per cubic foot (32 to 96 kg/m.sup.3). In addition, with the possible exception of fiberglass which may be used under certain conditions as a fire block, the common thermal insulating materials having fire block properties, such as carbon or graphite felts and ceramic materials, do not have any resiliency, i.e., they do not have the abilitity to recover from compression of the original "loft". Further, these prior art materials are not compressible from their original loft to any great degree since substantially straight or linear fibers do not have substantial distance between the fibers, thus there is very little loft between the linear fibers and therefore substantially no compressibility.
Both government and industry have conducted extensive research into developing fabrics that would either by non-flammable or at least retard the propagation of a fire. In conjunction with finding an effective material to act as a fire barrier, consumer considerations require that any such materials to be functional, aesthetically acceptable and reasonably priced.
Unfortunately, past efforts to develop a suitable fire barrier have not been very effective. Thus, even fabrics that will not ignite from a smoldering cigarette and that are considered to be class 1 fabrics under the UFAC upholstery fabric classification test will burn when placed in contact with an open flame. Consequently, this leads to the ignition of an underlying batting in a cushion or mattress.
So-called fire retardant foam coatings for draperies, liners and backcoatings for upholstery, as well as chemical treatments for apparel fabrics that attempt to provide a fire retardant quality to the fabric are commercially available. Unfortunately, these materials are, at best, self extinguishing only when the source of the flame is removed. If the flame source is not removed, these materials will char, lose their integrity and, most importantly, will not prevent the flame from reaching materials underneath the fabric covering which act as a major source of fuel for the fire.
Other attempts at solving the flammability problem have centered on the use of inherently non-flammable fabrics such as fiberglass which can be used, for example in draperies. It has been discovered, however, that the glass fibers are self abrasive in that they rub against each other thereby becoming self-destructing due to the abrasive action. Thus, hand washing and line drying is, out of necessity, the recommended cleaning procedure for such fabrics. Moreover, the brittle and broken glass fibers tend to be very irritating to the skin thus rendering any of the applications of the fabric unsuitable where there is extensive skin contact. Fiberglass fabrics usually contain flammable sizing binders and/or finishes to provide an aesthetic appearance.
Consequently, there is a need for fabrics, battings and the like which not only provide fire shielding properties but also are washable, light weight and can be fabricated into aesthetically acceptable fabrics for home and commercial use.
U.S. Pat. No. 4,588,635 to James. G. Donovan discloses light weight thermal insulation material which is a blend of spun and drawn, crimped, staple, synthetic polymer microfibers having a diameter of from 3 to 12 microns, and synthetic polymeric staple microfibers having a diameter of more than 12 and up to 50 microns. However, the insulation material is flammable.
U.S. Pat. No. 4,167,604 to William E. Aldrich discloses the use of crimped hollow polyester filaments in a blend with fowl down in the form of a multiple ply carded web which is treated with a thermosetting resin to form a batting having termal insulating characteristics. The web, however, does not have fire retarding characteristics.
U.S. Pat. No. 4,321,154 to Francois Ledru relates to high temperature thermal insulation material comprising insulating material fibers and pyrolytic carbon. To make the insulation light weight, an expanding agent is utilized that is composed of hollow particles such as microshperes.
European Patent Application 0199567 of McCullough, et al discloses non-linear carbonaceous fibers which are used in the structures and fabrics of the present invention.
The carbonaceous fibers of the invention according to the test method of ASTM D 2863-77 have a LOI value greater than 40. The test method is also known as "oxygen index" or "limited oxygen index" (LOI). With this procedure the concentration of oxygen in O.sub.2 /N.sub.2 mixtures is determined at which a vertically mounted specimen is ignited at its upper end and just continues to burn. The size of the specimen is 0.65.times.0.3 cm with a length from 7 to 15 cm. The LOI value is calculated according to the equation: ##EQU1##
The LOI values of different fibers are as follows:
______________________________________ polypropylene 17.4 polyethylene 17.4 polystyrene 18.1 rayon 18.6 cotton 20.1 nylon 20.0 polycarbonate 22 rigid polyvinyl chloride 40 stabilized polyacrylonitrile greater than 40 graphite 55 ______________________________________
The term "stabilized" herein applies to fibers or tows which have been oxidized at a specific temperature, typically less than about 250.degree. C. for PAN fibers, provided it is understood that in some instances the filaments or fibers are oxidized by chemical oxidants at lower temperatures.
The term "Reversible Deflection" as used herein applies to a helical or sinusoidal compression spring. Particular reference is made to the publication "Mechanical Design-Theory and Practice", MacMillan Publ. Co., 1975, pp 719 to 748; particularly Section 14-2, pages 721-24.